Despite opinions to the contrary, these data suggest that there has been no apparent increase in overall productivity per active author over the last decade. Instead, authors are using their authorship potential more wisely by becoming more collaborative in the way they work, which is driving an apparent inflation in each author’s productivity as well as author bylines. Instead, the underlying driver of the volume increase in articles published is simply the introduction of new entrants/authors into the market. That is not surprising, as the total population of researchers globally continues to rise every year, and they become increasingly subject to the principles of "publish or perish": and so the cycle continues.

This rise in ‘fractional authorship’ (the claiming of credit for authorship of a published articles by more than one individual) is most likely driven by research collaboration, and is an efficient mechanism by which each author can increase their apparent productivity from the same underlying research contributions (i.e. articles per unique author) of 0.56 articles per unique author per year.

Results of our analysis show that there has been a consistent growth in the number of articles published over the past decade; from 1.3 million in 2003 to 2.4 million in 2013 (see Figure 1). At the same time, the number of authorships has increased at a far greater rate from 4.6 million in 2003 to 10 million in 2013.

authorships are growing at a much faster rate than articles (though interestingly, "unique authors" are also growing at a faster rate than authors... though I think what they mean is the number of unique individuals identified as authors, however many times they are identified (= unique authors) vs. "number of names appearing in bylines (=authorships).

The phenomenon has become a focus of academic research itself, as a search for the phrase in Scopus retrieved 305 documents published on the topic from 1962 to date. On average, more than 20 articles per year were published on the topic over the past 5 years (2009 – 2013), with 37 articles alone published in 2013.